Conventionally, a substrate conveying robot with left and right arms is known as a substrate conveying robot for conveying a substrate such as a semiconductor wafer. Each arm of the substrate conveying robot has a first, link member rotatable about a pivot axis line, a second link member rotatably connected to a tip end portion of the first link member, and a substrate holding member (hand) rotatably connected to a tip end portion of the second link member.
For simplification of the robot structure or the like, one of the substrate conveying robots with the left and right arms is a substrate conveying robot in which a pivot axis line is shared the left and right arms (Patent Document 1). In the substrate conveying robot of this type, the first link member and the second link member are configured to be the same length, and also the left and right substrate holding members are arranged at different heights.
In contrast, when the pivot axis line is shared by the left and right arms and also the left and right substrate holding members are arranged at the same height in the substrate conveying robot, there is a problem that, when the first link member and the second link member are set to the same length, the second link members of the left and right arms interfere with each other or the second link member and the pivot axis line interfere with each other in changing the arms from their extended state to their contracted state.
In order to solve the problems of the interference between the second link members or the interference between the second link member and the pivot axis line, it is considered to set the length of the second link member shorter than the length of the first link member.
Note that, when the first link member and the second link member are set to the same length, a moving locus of the tip end portion of the second link can be linear by setting the rotational speed of the first link member about the pivot axis line and the rotational speed of the second link member about a first rotational axis line on the tip end portion of the first link member to 1:2.
Also, an attitude of the substrate holding member in the extension-contraction operation of the arms can be maintained constant so as to make a moving locus of the substrate holding member linear by setting the rotational speed of the second link member about the first rotational axis line and the rotational speed of the substrate holding member about a second rotational axis line on the tip end portion of the second link member to 2:1.